A non-binary turbo code is configured to output a parity bit for a plurality of bit input signals, in comparison with an early turbo code configured to output a parity bit for a 1 bit input signal. In order to encode an N-bit information sequence, two N/2-bit-length input sequences A and B are formed, and then the respective input sequences A and B are simultaneously inputted to an encoder. That is, the two types of bits are entirely inputted into the encoder at once. The non-binary turbo code is formed in parallel with two simple recursive systematic convolutional codes (RSCC), which form a parity symbol by utilizing a plurality of input bits at once in this manner.
It is known that the turbo code has superior performance to a convolutional code generally used in a current mobile communication environment for high-speed data. Accordingly, Korean patent application No 10-1999-0034719 (Samsung Electronics Company) entitled “Apparatus for inserting a known bit into a channel encoder and method thereof” discloses that a bit known at both the receiver and transmitter is inserted into a turbo encoder as input values.
FIG. 1 is a block diagram using a non-binary turbo encoder according to the prior art.
A non-binary turbo code shown in FIG. 1 is configured to generate a parity bit for a plurality of input bits. That is, an information bit sequence is divided into two identical length sequences. The respective two information sequences configured in this manner provides simultaneously one bit, that is, two-bit signals into one RSCC.
One pair of the input signals is passed through a first configuring encoder 10 to be given as a first parity bit sequence Yk, and the other pair of the input signals is inputted into a Convolutional Turbo Code (CTC) interleaver 20 to be converted into interleaved signals. The interleaved signals are passed through a second configuring encoder 30 to be given as a second parity bit sequence Wk.
The first parity bit sequence Yk and the second parity bit sequence Wk are encoded in this manner and inputted to a multiplexer 40. In this case, the original information bit sequences Ak and Bk are also inputted in the multiplexer 40. In order to provide various code rates, encoded data can be generated by punching holes in the first parity bit sequence and the second parity bit sequence.
FIG. 2 is a configuration diagram using a non-binary turbo encoder of a code rate of ⅓ according to the prior art.
A method for coding a channel at a low code rate has been recently required so as to avoid a strong interference environment from adjacent cell users in a communication system. Accordingly, as shown in FIG. 2, when the encoder of a code rate of ⅓ is used, the encoder is used two times to generate a code rate of ⅙ to be used, and four times to generate a code rate of 1/12 to be used.
A non-binary turbo encoder with the code rate of ⅓ is generally used, and is obvious to an ordinary skilled person in the art. Accordingly, a detailed expression of the encoder will be omitted.
Since the conventional turbo encoder actually has the code rate of ⅓ and a multiplexer is used to remove all but the desired information bit sequences, a polynomial expression for generating a more parity bit, that is, a feedforward loop is to be added in a communication environment to encode the information bit sequences at a lower code rate than the current code rate of ⅓. Accordingly, there is a problem in that the lower code rate has a less enhanced performance in comparison with the parent code rate of ⅓ due to repeating the encoded information bit sequence.
Also, since the performance depends on the information bit sequence, there is a problem in that the repeated codes have a bad effect when the length of the information bit sequence is short.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.